Medical tubing or tubes are commonly inserted into humans or animals for therapeutic and diagnostic medical procedures. Surgeons or other medical professionals must often be able to determine the specific distance that the medical tubing is inserted into a body of a patient. The accurate placement of the medical tubing is usually critical to the procedure. If medical tubing is inserted too far into a patient, it could tear, puncture, or otherwise cause damage to internal bodily tissues, vessels, and/or organs, which could be harmful or potentially fatal to the patient. Alternatively, if not inserted far enough, the procedure may not be successfully performed. Accordingly, certain medical tubing is marked with visual indicia of one or more colors at measured intervals along the length of the medical tubing to indicate to the user the length, orientation, size, or diameter of the medical tubing inserted into a patient. For example, to assist the surgeons or other medical professionals, directional arrows and/or bands of various colors are often marked on a surface of the medical tubing to enable the surgeon to denote orientation of the medical tubing.
One potential problem with such medical tubing is that the markings placed at measured intervals along the length of the medical tubing may be inaccurate. That is, such markings may be slightly misplaced (i.e., are not placed at the exact location along the length of the medical tubing indicated to the medical professional). For example, a marking that is supposed to indicate to a medical professional that a mark is 2.00 inches (or 5.08 centimeters) from a distal end of the medical tubing may be misplaced and actually be 2.10 inches (or 5.33 centimeters) from the distal end of the medical tubing. In the medical industry and specifically in the field of medical tubing that is inserted into a patient's body, such inaccuracies may be harmful or potentially fatal. In other words, when marked medical tubing is inserted into a body, such slight inaccuracies in the placement of the indicated marking may cause the medical tubing to be inserted too far into a patient (which is associated with the above-described risks to the patient) or not far enough into a patient (which is associated with the above-described risks to the patient). Accordingly, accurate placement of markings along the length of medical tubing is critical when such medical tubing is inserted into a patient.
Additionally, certain known medical tubing can “stick” to tissues, catheters, or other surfaces during insertion or extraction. If medical tubing sticks to other surfaces as it is inserted into a body, the surgeon or other medical professional must apply a greater insertion force to the medical tubing to reinitiate movement. Once movement is reinitiated, the opposing force immediately decreases so that the medical tubing is caused to quickly accelerate into or out of the body. Such extreme movements increase the risk of scraping, rubbing, tearing, puncturing, or otherwise damaging a patient's internal tissues due to misplacing the end of the medical tubing in the patient.
To address such issues, certain know medical tubing has been formed from one or more low-friction, low surface energy materials, such as polytetrafluoroethylene (PTFE). This medical tubing, such as solid PTFE tubing, non-solid PTFE tubing, cellular PTFE tubing, porous PTFE tubing, and expanded PTFE tubing (known commonly as e-PTFE), reduces the amount of friction between the medical tubing and bodily tissues, catheters, or other surfaces. Accordingly, such low-friction medical tubing is less likely to stick to other surfaces and therefore gives surgeons or other medical professionals more control over the insertion speed and depth, which reduces the risk of harm to the patient by reducing the above-described “slip-stick” phenomena. Such low-friction medical tubing generally has a smooth very slippery outer surface that will not scrape, irritate, or snag tissues, vessels or arteries. However, because of the extremely low surface energy of the smooth, very slippery low-friction surfaces of such medical tubing, there are very limited methods for securely placing and permanently adhering markings on such low-friction medical tubing, such as PTFE tubing.
One known method of marking low-friction medical tubing and specifically PTFE tubing, is to print or otherwise deposit ink (or paint) on the surface of the low-friction medical tubing and then cure the deposited ink at a cure temperature that does not affect or otherwise degrade the PTFE tubing. For example, for tetrafluoroethylene-hexafluoropropylene (FEP) Striping Ink manufactured by Colorant Chromatics, Colorant Chromatics recommends applying the FEP Striping Ink on a PTFE substrate and curing the applied FEP Striping Ink at 509° F. (265° C.). In another example, for GEM® WB1150 High-Temp Striping Ink manufactured by GEM®, GEM® recommends applying the High-Temp Striping Ink to a PTFE substrate and curing the applied High-Temp Striping Ink at 509° F. (265° C.). In another example, for GEM® WB1140 High-Temp Marking Ink manufactured by GEM®, GEM® recommends applying the High-Temp Marking Ink to a PTFE substrate and curing the applied High-Temp Marking Ink at 509° F. (265° C.).
It should be appreciated that the cure temperature of each of these inks is at or below 550° F. (288° C.) because while PTFE has a melting temperature of 621° F. (327° C.), PTFE begins to decompose or break down as the PTFE is heated to temperatures above 500° F. (260° C.). Such decomposition of the PTFE can generate toxic or noxious gasses and other harmful airborne particles. Specifically, DuPont™ (i.e., a manufacturer of PTFE) expressly warns that PTFE should not exceed 500° F. (260° C.) and that fumes released by PTFE heated above 500° F. (260° C.) can produce symptoms referred to as “polymer fume fever”. Accordingly, to avoid the PTFE decomposing and emitting harmful byproducts, known methods of marking PTFE tubing with inks (or paints) expressly require that the inks or paints be cured at a temperature below the temperature which PTFE begins to decompose and possibly emit harmful byproducts.
It should be further appreciated that when PTFE tubing is heated to temperatures above 500° F. (260° C.), not only can the PTFE begin to decompose, but the dimensions of the PTFE tubing can begin to change. That is, the PTFE tubing can warp, distort, contract or otherwise shrink due to such temperatures. This warping of the PTFE tubing may result in the uncured or wet ink (or paint) markings previously placed at correct measured intervals along the length of the PTFE tubing prior to curing to become inaccurate and misplaced (i.e., not placed at the exact location along the length of the PTFE tubing indicated to the medical professional). As described above, for medical tubing that is inserted into a patient's body, such inaccuracies may be harmful or potentially fatal. Accordingly, to avoid these undesired dimensional changes (and potential accompanying inaccuracies in the placement of markings) to PTFE tubing that occur when PTFE tubing is heated to temperatures above 500° F. (260° C.), known methods of marking PTFE tubing with inks (or paints) heat the PTFE tubing below the temperature which PTFE tubing begins to warp or otherwise shrink.
In light of the known problems with heating PTFE to temperatures at or above the temperature which PTFE begins to decompose and warp, known methods of marking PTFE tubing is to print ink or otherwise deposit ink on the surface of the PTFE tubing and then cure the deposited ink to a temperature below the temperature which PTFE begins to decompose and warp. However, one known problem with marking this low-friction medical tubing is that the marked medical tubing (formed from PTFE which is a low-friction, low-surface energy, relatively inert and very slippery material) resists bonding with such inks (or paints). That is, because the bond strength of the ink to the low surface energy PTFE surface is very weak, the slippery surface of this low-friction medical tubing often allows inks printed on this type of medical tubing to easily peel or flake off the tubing (e.g., the ink can generally be scratched off with a human fingernail rubbing the deposited ink). If the ink (or paint) peels or flakes off or dislodges inside a patient's body, such ink (or paint) may harm the patient (as the ink is not as inert as the PTFE tubing). Ink may also rub or peel off before or during use of the medical tubing, thus destroying the usefulness of the markings, and increasing the risk that the medical tubing will be inserted either too deep, or not deep enough (and harm the patient and/or render the medical procedure ineffective).
Furthermore, many types of commercially available medical tubing have a relatively small outer diameter such that even thin layers of ink can significantly increase the measurable total outer diameter of the medical tubing. By significantly increasing the outer diameter of certain marked portions of the medical tubing and not increasing the outer diameter of certain other unmarked portions of the medical tubing, grooves or valleys can be created in the outer surface of the low-friction medical tubing. The shoulders of these bumps or protrusions can have relatively sharp edges which can scrape or irritate bodily tissues, snag vessels or arteries of the patient, or otherwise cause damage and/or trauma to the patient. When inserting medical tubing into delicate areas, such as various organs, the brain and/or the heart, damage caused by even the smallest of such bumps or protrusions can be harmful and potentially fatal for the patient. Additionally, creating different outer diameters along the length of the medical tubing tends to increase the required insertion force and decreases the control a surgeon or other medical professional can exercise over the speed and depth of an insertion. Therefore, such known methods of marking low-friction medical tubing adversely affects the function of the low-friction medical tubing.
Accordingly, a need exists for improved markings on low-friction medical devices, and specifically medical devices made from PTFE and blends of PTFE polymers. More specifically, a need exists for improved markings on solid PTFE medical tubing, non-solid PTFE medical tubing, expanded PTFE medical tubing (known commonly as e-PTFE), porous PTFE medical tubing, and/or cellular PTFE medical tubing. Such a need exists for such low-friction medical tubing with markings that are permanently bonded to the surface of the low-friction medical tubing, that are indelible (i.e., not readily or easily removable by solvents or liquids and relatively abrasion resistant), that are accurately placed on the low-friction medical tubing, that do not significantly increase or decrease the diameter of the low-friction medical tubing (i.e., do not significantly protrude from the surface) and that do not significantly adversely affect the function of the low-friction requirements of medical tubing.